Fats and oils are essential for a human body as nutrients and source of energy supply (the primary function), and moreover, are important for providing so-called sensory function (the secondary function), which satisfies palatability of foods, for example, taste or aroma. In addition, fats and oils containing diacylglycerols at a high concentration are known to show physiological effects (the third function) such as body fat-burning effect.
Untreated fats and oils obtained by compressing plant seeds, germs, fruit pulps, and the like contain fatty acids, monoacylglycerols, odor components, and the like. Further, in processing the fats and oils, minor components are produced as by-products through heating steps such as transesterification reaction, esterification reaction, and hydrogenation treatment, thereby impairing taste and flavor. In order to use the fats and oils as edible oils, it is necessary to improve the taste and flavor by removing these by-products. Thus, treatment of so-called deodorization, in which the fats and oils are brought into contact with water vapor under reduced pressure at high temperature, is generally performed (Patent Document 1).
In addition, in order to improve the taste and flavor in diacylglycerols-rich fats and oils, there have been reported a method involving adding an organic acid to diacylglycerols-rich fats and oils and subsequently subjecting the fats and oils to decolorization treatment using a porous adsorbent and deodorization treatment (Patent Document 2) and a method involving hydrolyzing raw material fats and oils by an enzymatic degradation method to produce fatty acids and glycerin, subjecting the fatty acids and glycerin to esterification reaction, and subsequently subjecting the resultant products to deodorization treatment so that deodorization time and deodorization temperature fall within specific ranges (Patent Document 3).